This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines combust a mixture of air and fuel to generate torque. The fuel may be a combination of liquid fuel and vapor fuel. A fuel system supplies liquid fuel and vapor fuel to the engine. A fuel injector provides the engine with liquid fuel drawn from a fuel tank. An evaporative emissions system, typically including, but not limited to, a fuel tank, a vapor canister, a vent valve, a purge valve, and maybe a purge pump, provides the engine with fuel vapor drawn from the fuel tank and vapor canister.
The liquid fuel stored within the fuel tank may vaporize and form fuel vapor. The vapor canister traps and stores the fuel vapor to prevent it from escaping into the atmosphere from the system. It is known that fuel vapor may sometimes escape into the atmosphere through small leaks in the system, e.g., at the gas cap or other means, that can contribute to air pollution.
Some system tests for fuel vapor leaks rely on heat generated from the engine to produce changes in pressure when the system is closed. However, future fuel efficient engines that produce a low heat signature, may not provide the heat necessary to generate enough pressure for running a leak test. It is desirable to have a fuel vapor leak test suitable for future fuel efficient vehicles having low heat signature engines.